1. Field of the Invention
The present invention pertains to improved methods for insert molding a laminated film or the like over a plastic substrate and to fused film-plastic parts made thereby.
2. Description of the Related Art
A variety of injection molded parts have been made and used for automobile body and trim parts. For example, bumpers, body panels, doors, filler panels, wheel covers, dashboards, arm rests and other parts have been made via injection molding techniques. Additionally, with regard to automobile exteriors, body side moldings, beltline moldings, roof moldings and window moldings have been made via injection molding of polyvinylchloride (PVC) or other thermoplastic materials.
In order to provide a painted surface for these parts, film lamination techniques have been successfully employed. In accordance with these processes a paint film laminate is insert molded with the desired thermoplastic to fuse the film over the injection molded part. The resulting injection molded part is ready for assembly without subsequent painting.
The paint film laminate used in these insert molding techniques may comprise a backing sheet of about 0.020" in thickness to which paint layers are adhered to form a colored side of the laminate. Typically, the backing sheet comprises an extruded thermoplastic sheet.
In such paint film laminates, a paint film, comprising a cast dried continuous paint coating, is provided over the backing sheet. The paint film may consist of a monocoat, a clear coat over a base coat or a clear coat and a base coat with interposed print or design. The paint film, including base coat, clear coat and print or design, if desired, may range from about 0.5-4 mil. in thickness.
The laminated paint films are available, for example, from Avery Dennison, Automotive Division or Rexham Decorative Products, Charlotte, N.C. The films are typically provided in a roll, unwound, then trimmed to a proper "preform" size and shape, ready for insertion into the injection mold. The preform is usually placed along the cavity side of the mold with the painted side thereof facing the mold cavity surface. In some instances, the preform may be placed along the core side of the mold. The mold is then clamped and the desired molten resin is injected into the mold cavity. Heat and pressure conditions in the mold partially melt the backing sheet and a melt bonding or fusion of the injected resin and film occur. Injection molds used for these processes are rear or edge gated so that the molten resin is directed along the backside of the film.
Although these processes provide significant advantage, they are not without problem. For example, edgewise portions of the part, such as the longitudinally extending edges of elongated strips used for body moldings, may not be completely covered with the film. Accordingly, these edges reveal the uncovered plastic substrate and provide an aesthetically displeasing appearance since the continuity of the painted surface is interrupted by the unsightly appearance of the underlying plastic substrate.
Techniques for preforming paint film laminates and insert molding laminated plastic parts are disclosed in U.S. patent application No. 08/372,230 to Yamamoto, filed Jan. 13, 1995, and U.S. Pat. application No. 08/393,169 to Yamamoto, filed Feb. 21, 1995. The disclosure of both applications is incorporated herein by reference. Nonetheless, there remains a need in the art for improved methods for insert molding of a film laminate over a plastic substrate in such manner that the longitudinal edge portions of the substrate are covered by the film.